OP -> you are right not to transport any extra kids in your car.

You should ask the MB for a heads up about kids coming around for a play date "hey it would be great to know ahead of time if X has someone coming around for a play date so I don't arrange an activity or outing for that time/day"

I half agree with you. I don't mind hosting playdates, in fact I think it makes me job easier. If the kids are younger it also means some adult company as well (which I almost always enjoy). I would be grumpy if the playdates were not reciprocated though, because it sucks to be responsible for extra kids all the time.

I think your attitude towards the playdates is wrong though - you don't get paid extra to look after the extra child, because sometimes your charge should be going over to the other childs house, so you will have one less child sometimes.

PLZ TELL ME YOU SAID NO.

"I wanted to make sure I should not have to entertain them all the whole time if they are here "

hunh?? DD is 5 and she virtually disappears during playdates. They occassionally need some intervention if bickering arises but mostly they play well and it means I am "relieved" of entertaining DD at all during the playdate. I would imagine 7 year olds are even more independent. How is this not EASIER for you, OP? (I honestly don't mind hosting playdates on the weekend since i have a younger DC and so am house-bound anyway often. the playdate makes less work for me since then the oldest is happily engaged w/ someone else and I can focus easier on the youngest.)

So if you were paid extra, you'd engage with the kids? You sound like a bitch.

You sound like a horrible nanny. A second grader needs playmates for social interaction and though he doesn't need you engaged it's not appropriate to tell them to entertain themselves. It's a job!